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My Robotic arm is not moving when I give the x and y and z values to form a pose goal, What to do? I get the following errors. [Error] Unable to sample any valid states for goal tree

asked 2018-09-27 06:50:50 -0600

mvkzenith gravatar image

I use python code to provide pose goals with Orientation and Position values It works for the example urdf models and the arm moves to the desired pose, but I use my own model exported as urdf from solidworks. What to do with the error? Help me with a solution!

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answered 2018-09-27 11:47:06 -0600

mvkzenith gravatar image

updated 2018-09-27 11:50:16 -0600

When I try to move the Arm using Python code, I get the following output

============ Starting tutorial [ INFO] : Loading robot model 'pi_robot'...

[ INFO] : Loading robot model 'pi_robot'...

[ INFO] : Ready to take commands for planning group base_arm.

============ Reference frame: /base_rotary

============ Robot Groups:

['base_arm', 'claws']

============ Printing robot state

joint_state: header: seq: 0 stamp: secs: 0 nsecs: 0 frame_id: "/base_rotary" name: [base_rotary3, rotary_biceps, biceps_forearm, Forearm_wrist, wrist_rotary_claw, claw_gripper_1, claw_gripper_2, link_claws] position: [-0.9492579224650748, 0.23973554670321753, 0.9810336592943874, 0.20257978661255913, 0.3314634015831165, 0.0, 0.0, 0.0] velocity: [] effort: [] multi_dof_joint_state: header: seq: 0 stamp: secs: 0 nsecs: 0 frame_id: "/base_rotary" joint_names: [] transforms: [] twist: [] wrench: [] attached_collision_objects: [] is_diff: False

============

============ Waiting while RVIZ displays plan3...

And Rviz gives the following Output

[ INFO] : Planner configuration 'base_arm' will use planner 'geometric::RRTConnect'. Additional configuration parameters will be set when the planner is constructed.

[ INFO] : RRTConnect: Starting planning with 1 states already in datastructure

[ERROR] : RRTConnect: Unable to sample any valid states for goal tree

[ INFO] : RRTConnect: Created 1 states (1 start + 0 goal)

[ INFO] : No solution found after 5.004745 seconds

[ INFO] : Unable to solve the planning problem

[ INFO] : Combined planning and execution request received for MoveGroup action. Forwarding to planning and execution pipeline.

[ INFO] : Planning attempt 1 of at most 1

[ INFO] : Planner configuration 'base_arm' will use planner 'geometric::RRTConnect'. Additional configuration parameters will be set when the planner is constructed.

[ INFO] : RRTConnect: Starting planning with 1 states already in datastructure

[ERROR] : RRTConnect: Unable to sample any valid states for goal tree

[ INFO] : RRTConnect: Created 1 states (1 start + 0 goal)

[ INFO] : No solution found after 5.009016 seconds

[ INFO] : Unable to solve the planning problem

[ INFO] : Received event 'stop'

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These error messages are telling you that the planner can't find a solution to that pose using your robot arm. In a nut shell your arm cannot reach that goal pose.

PeteBlackerThe3rd gravatar imagePeteBlackerThe3rd ( 2018-09-27 12:08:36 -0600 )edit

I can Understand that! I want to know why? What's the solution for this?

mvkzenith gravatar imagemvkzenith ( 2018-09-27 12:49:44 -0600 )edit

Start by trying some different poses. Maybe a little bit closer to the robot.

AndyZe gravatar imageAndyZe ( 2018-09-27 13:38:34 -0600 )edit

poses are working, But when I give the following, it is not working

pose_goal = geometry_msgs.msg.Pose()
pose_goal.orientation.w = 1
pose_goal.position.x = 0
pose_goal.position.y = 0
pose_goal.position.z = 0
group.set_pose_target(pose_goal)

plan1 = group.plan
mvkzenith gravatar imagemvkzenith ( 2018-09-27 13:58:22 -0600 )edit
1

(0,0,0) is likely inside the base of the robot --> collision. Again, try a different pose. I think you can do get_planning_frame() to see what your coordinate frame is.

AndyZe gravatar imageAndyZe ( 2018-09-27 16:43:44 -0600 )edit

============ Reference frame: /base_rotary ============ Robot Groups: ['base_arm', 'claws'] ============ Printing robot state

Tried with different pose! (2,2,2)

mvkzenith gravatar imagemvkzenith ( 2018-09-28 04:14:09 -0600 )edit

[Error] Orientation constraint for link 'claw_motor' is probably incorrect: 0.000000, 0.000000, 0.000000, 0.021194. Assuming identity instead.

WHat about this?

Panda Arm is working when I give a Valid Point, But not My arm. WHy?

I will upload my URDF?

mvkzenith gravatar imagemvkzenith ( 2018-09-28 08:36:03 -0600 )edit
2

I don't believe those values correspond to a valid Quaternion, that is probably why you get that warning.

gvdhoorn gravatar imagegvdhoorn ( 2018-10-01 04:03:40 -0600 )edit
2

answered 2018-09-27 09:52:18 -0600

AndyZe gravatar image

updated 2018-09-27 10:39:22 -0600

Can you post the full error message? It may be that 2 links are in collision because they weren't aligned exactly, or the collision should be disabled in the SRDF but it's not. (So check your srdf file)

It could also be that an initial joint angle is outside the allowable range.

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Collision is disabled in SRDF

What is meant by the Initial Joint Angle?

mvkzenith gravatar imagemvkzenith ( 2018-09-28 08:37:27 -0600 )edit

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Asked: 2018-09-27 06:41:22 -0600

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Last updated: Sep 27 '18